Secondary cells or batteries well known in the prior art include nickel-cadmium batteries, lead-acid batteries, and the like. However, they have a common drawback, in that the energy density per unit weight, or unit volume, is comparatively low.
One solution that has been proposed is a nickel-hydrogen cell or battery in which the negative electrode is an electrode made of a hydrogen-occlusion alloy capable of electromechanically occluding and releasing a large quantity of hydrogen.
The positive electrode is made of a nickel oxide and the electrolyte is an alkaline aqueous solution, thus giving a higher energy density. In such a cell the negative electrode is composed of a hydrogen-occlusion alloy such as LaNi.sub.5.
However, in the case of the above-mentioned hydrogen-occlusion alloy, it is difficult for it to electrochemically occlude hydrogen sufficiently under atmospheric pressure, because its hydrogen dissociation pressure at room temperature is more than 2 atmospheres. Furthermore, its service life is very short, only about 30 cycles or so, in terms of repeated charge-discharge cycles. These shortcomings combine to make it a rather impractical solution.
The electrode of this invention provides a practical solution to the problems described above and comprises a new and heretofore unknown composition which is extremely effective and readily fabricated.
It is therefore an object of this invention to provide a new hydrogen-occlusion alloy electrode which is capable of occluding hydrogen under atmospheric pressure.
It is a further object of this invention to provide an improved hydrogen-occlusion alloy electrode which gives a large discharge capacity and has a long life.
Further and other objects will become apparent upon consideration of the detailed description of the preferred embodiment of the present invention.